Recent reports of the occurrence of sporadic symptomatic rotavirus strains bearing the M37-like VP4 gene have stimulated interest regarding the putative attenuated nature of neonatal rotaviruses. A number of these strains are at present being adapted to tissue culture. The nucleic acid sequence analysis of these strains associated with symptomatic infection in neonates may provide data which would help to explain the obscured attenuated nature of the majority of rotavirus strains recovered from neonates who are infected in newborn nurseries.